Device to balance thrust in turbines.



Witnesses A. BARBEZAT.

DEVICE T0 BALANCE THRUST IN TURBINES.

APPLIOATION FILED JULY 10, 1911.

Patented June 18, 1912.

ALFRED BARBEZAI', 0F LESQUIN, NEAR LILLE, FRANCE.

DEVICE T0 BALANCE THRUST IN TURBINES.

Specification of Letters Patent.

Patented June 18, 1912.

Application filed July 10, 1911. Serial No. 637,766.

To all whomit may concern! Be it known that I, ALFRED BARBEZAT,

the combined action of steam, admitted be hind the rear bottom of theturbine drum, with one or more packing rings which participate in theaxial displacement of the drum and increase or diminish the sectionthrough which said steam is admitted behind the bottom of the drum;therefore increasing or diminishing the pressure .on said bottomproportionally to the increase or decrease of axial thrust.

The invention is illustrated by way of example in the accompanyingdrawings in which- Figure 1 is a sectional view of a construction of aknown device. Fig. 2 is a sectional view of the device according to theinvention. Fig. 3 is a diagram of a development of the cross section ofFig. 2.

In Fig. 1 of the drawing, which is a particular construction of a knownform of device, A B designates that part of the turbine drum which isprovided with moving blades. As known, steam, when passing throughdifferent stages of blades, relaxes progressively from the boilerspressure to that of the condenser, thus causing an axial thrust in thedirection of the arrow CD.

To balance this axial thrust a set of pack ing rings is provided in Eand a certain pressure caused to act on the rear G of the drum. Thispressure is regulated by throttling more or less the annular space mthrough which steam is admitted to act on the rear side G of the drum.To this purpose there are provided one or more packing rings R,conveniently disposed and which, for example, as in the drawing, arefixed on to the shaft of the drum in order to participate in itsmovement due to the axial thrust. The steam which is to act against therear of the drum is admitted into the space N behind the packing rings R(of which one only is shown in the drawing) whence it passes through theannular space m whose section varies according to the relative positionof R and of the part a of the casing. The steam under pressure is ledinto the space N by means of any external pipe L.

The above described device works as follows: If, owing to theaxial-thrust of the drum, said drum is shifted in the direction CD shownby the arrow in the drawing, the packing-rings R fixed on to the turbineshaft are shifted in the same direction, thus causing an immediateincrease of the section of the annular passage m and therefore also anincrease ofthe pressure on the rear G of the turbine drum; this pressureis opposite in direction to that shown by the arrow CD and increasesuntil it equals the latter. Should the drum, for any reason, be shiftedin the opposite direction to that indicated by the arrow C D, thesection of the annular space m will decrease according to thedisplacement of the drum and therefore practically no more steam will beadmitted behind the rear bottom of the drum, thus allowing thelow-pressure steam in B to pass through the packing rings E and enterthe space behind G; the counter-pres sure thus diminishes and the axialthrust whose normal direction is that of the arrow CD shifts the drumback toward the right. Such a construction would in practice show agreat disadvantage, in fact, the. slightest axial displacement of therotating part of the turbine causing great variation of the balancingpressure of the rear of the drum G, the rotor would oscillate axiallyand therefore the moving part R would press against the fixed part S ofthe casing and owing to this friction these parts should soon wear outand an accurate balancing of the axial thrust become impossible.

The construction according to the invention which is shown in Fig. 2obviates entirely the above stated disadvantage. A collar-ring R with ascrew like or inclined face is keyed on the motor shaft and turns infront of a fixed circular part S, whose position can be regulated atwill by the pro vision on the said fixed part S of a screw thread.WVhen, owing to the axial thrust of the drum, the ring It is shifted inthe one or the other direction, the steam is throttled as necessary bythe collar-ring R closing up more or less the inclined opening m withoutboth parts R and S touching each other in any case. The Working of thisdevice, together with a constant throttling device shown at a,eliminates totally the axial oscillations of the rotor.

The diagram Fig. 3 is the development of the cross section; in saiddiagram X is the section of passage of the steam and s the totaldisplacement of the collar-ring R in relation to the fixed part S. Theline T U instead of being oblique, could be broken or curved in anymanner.

The steam to balance the axial thrust is led through I to G and itsthrottling in a, between I and G, slackens slightly the balancing eifecton G and eliminates totally the axial oscillations of the rotor. Owingto the above described device, thrust bearings can be dispensed with.The axial position of the rotor with respect to the turbine casing canbe regulated by means of the part S secured by means of the nut M.

Having thus described and ascertained the nature of my invention and inwhat manner it has to be performed, What I claim is:

In a steam turbine, an automatic device to balance the axial thrustcomp-rising, in combination, an automatically working throttling devicelocated behind the rear of the turbine-drum and consisting of a rotatingcollar-ring with a screw-like or inclined face keyed on the turbineshaft and of a fixed circular part of smaller external diameter than theinner diameter of the collarring, means for regulating the axialdistance between said fixed part and the rotating collar-ring, means foradmitting steam under pressure in the annular space between the fixedpart and the rotating collar-ring of said automatic throttling deviceand a constant steam throttling device located be-- tween the rear ofthe turbine-drum, and the automatic throttling device all for thepurpose specified and substantially as set forth.

ALFRED BARBEZAT.

Witnesses EDOUARD LUGNEL, CHRISTOPHER J. KING.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

Washington, D. C.

